Week 9 - Attachment Feature Creation - Challenge 2
AIM: Create the Screw boss and Dog House for the Centre console coin holder considering the design rules mentioned in the video.
OBJECTIVE:
- Create a tooling axis following the OEM standard
- Making the Rib According to design rules
- Part Thickness : 40% NOMINAL VALUE and Draft angle : 0.5 Deg
- Performing the draft analysis to the component General guidlines of screw boss:
- Draft - 0.5 degrees on walls of boss
- Thickness - Typically 40%* of the nominal wall at the base.
- Height to Diameter Ratio - 3:1
- Radii - 0.25mm maximum radii.
"C" is where the doghouse contacts the backside of the surface
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Doghouse wall thickness at the intersection of the part wall ( C ) should be 40% or less than the main wall stock ( T ).
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Height of ( B ) should be between 3.0 – 6.0 mm
DOG HOUSE DESIGN:
Extract the base of class 'A' surface and offset it with part thickness as 2.5mm.
Draw sketch of rectangle and should be open from one side for dog house.
Using sweep with tooling direction and draft it at an angle of 1.5 degree for outer surface.
Close the upper surface face.
Give thickness in outer direction as 2.5mm or part thickness.
Now for the inside faces of dog house we need side core tooling axis, create it in Z-direction.
Give draft to the inside surface of 0.5 degree.
Now to create the 'C and B' section as shown in design rules, offset the base surface in between 3 to 6mm.
Extrapolate the surface to achive desired length.
Switch to part workbench and split the 'C and B' section with thicken part.
Again provide draft to the inside surface as shown.
Give radius/ fillet to inside as 0.4*T = 0.4*2.5 = 1 mm and for outer edges give fillet as inside radius + part thickness.
And minimum fillet of 0.5mm.
Assemble with coin holder main body.
Draft Analysis of Dog House
SCREW BOSS DESIGN:
- Creating the Screw Boss on the Coin holder:
Step: 1
Creating the sketch by extracting the class A surface, by each surfaces separately, point and axis system created simultaneously on the surface. Using positioned sketch making as shown below.
Step: 2
The sketch extruded to surface for minimal distance from the extract of coin holder as shown below.
Step: 3
The rib has been created by same procedure by sketch and extruding for supporting the screw boss and it is drafted for 0.5 deg.
Step: 4
It is assembled to main body and it is filleted for radius 0.25 of smooth edges as shown below.
Step: 5
Analysing the Rib root thickness for the coin holder rib by creating intersection for the model as shown below.
Finally we have created Screw boss with rib supported to the coin holder has shown below.
- Performing Draft Analysis:
The Draft Analysis command enables you to detect if the part you drafted will be easily removed. This type of analysis is performed based on colour ranges identifying zones on the analysed component where the deviation from the draft direction at any point, corresponds to specified values. This rule of thumb applies to parts with mold depths of up to 2 inches. At this size, draft as low as 1½ degrees will allow for an easy, non-damaging release from the mold when the expected shrinkage of the thermoplastic material occurs.
It’s also important to remember that draft angles are just one component of an effectively designed injection molded piece. Design for manufacture is one of the easiest ways to improve the quality and efficiency of your injection molding process, and it never hurts to stay up to speed on all injection molding best practices.
- Draft Analysis for Screw Boss formation:
Step: 1
First we have to set the compass on the main tooling axis to get the direction of core and part moves along as shown below.
Step: 2
Once compass is locked in the axis, directly click on the surface it will appear quality of draft surface whether, it is pass or failed. Here the draft angle is given as 0.5 degree. Hence we achieved green colour on top surface. Hence it accepts the draft angle for the surface, so we build good quality component.
Step: 3
Now we check colour variant scale to ensure the maximum and minimum area draft angle is achieved by displaying by green, red and blue colour respectively. If the surface appears red in colour while analysing it is not accepted.
Step: 4
We can check the angle of draft given to surface by using draft tool analysis just point the over the surface where we have check angle of given draft to the component as shown below.
Conclusion:
Creation of the Screw Boss and dog house on coin holder has been successful done by guidance of design rule. It has been converted from surface into solid body. The tooling axis has been created according the OEM standard. Drafting Analysis has been performed and results has been updated in step by step.